1. Field of the Invention
The present invention relates to footwear. The invention concerns, more particularly, an article of footwear having a lightweight sole structure formed of two coextensive plates.
2. Description of Background Art
The success of an athlete during modern athletic competitions is often dependent upon distances on the order of millimeters and differences in time that are measured in hundredths of a second. The overall weight of an athlete, which includes the weight of the athlete""s apparel and footwear, substantially affects the performance and success of the athlete during competitions. In order to gain an advantage over competitors, athletes often select footwear that performs in accordance with the demands of modern athletic standards, but with decreased weight when compared to other articles of footwear designed for the same purpose.
Conventional articles of footwear include two primary elements, an upper and a sole structure. The upper comfortably and securely receives the foot and is often formed of multiple layers of foam, leather, and textile materials that are stitched and adhesively bonded together. The sole structure is typically formed of multiple layers, including a midsole and an outsole. In addition, the sole structure may include an insole that is generally located within the upper and adjacent to the sole of the foot in order to enhance the comfort of the footwear.
The midsole forms the middle layer of the sole and often includes a resilient, foam material, such as polyurethane or ethylvinylacetate, that attenuates impact forces and absorbs energy when the footwear makes contact with the ground. That is, the compressive properties of the midsole act to reduce forces experienced by the foot during competitions. In general, an increase in midsole thickness also increases the force attenuating and energy absorbing characteristics of the midsole. In a detrimental sense, however, an increase in midsole thickness also increases the weight of the footwear and decreases the stability of the sole structure. In designing footwear midsoles, therefore, footwear manufacturers attempt to achieve a suitable balance between forces experienced by the foot, overall weight of the midsole, and stability. In order to increase the force attenuating and energy absorbing properties of midsoles without substantially increasing weight or decreasing stability, many modern midsole structures incorporate a fluid-filled bladder, as disclosed in U.S. Pat. Nos. 4,183,156 and 4,219,945 to Marion F. Rudy.
The outsole is attached to the lower surface of the midsole and is usually fashioned from a durable, wear-resistant polymer. The outsole functions as the ground-engaging surface of the footwear and often includes texturing to provide the footwear with traction, or resistance to slipping. Outsoles designed specifically for track and field running competitions may also include a spike plate that is attached to the outsole in at least the forefoot region. The spike plate includes a series of recesses that receive removable metal spikes for supplementing the traction properties of the outsole.
Based upon the above discussion, the sole structure of certain conventional articles of footwear includes two primary elements, a midsole and an outsole, that combine to provide the footwear with two fundamental characteristics. That is, the midsole attenuates impact forces and absorbs energy, and the outsole provides traction. In footwear designs where the midsole and outsole do not provide an optimum degree of force attenuation, energy absorption, or traction, the sole structure may also incorporate addition elements, such as a fluid-filled bladder and spike plate. The plurality of components that comprise modem sole structures may be inefficient to manufacture and have the potential to detrimentally affect the performance of an athlete by adding weight to the footwear.
The present invention relates to an article of footwear that includes an upper for receiving a foot of a wearer and a sole structure. The sole structure includes a moderator plate and a traction plate. The moderator plate is attached to the upper and the traction plate is attached to the moderator plate. The traction plate includes a plurality of upward projections and a plurality of downward projections that are structured to attenuate impact forces and absorb energy when the footwear contacts the ground. The upward projections are attached to the moderator plate, and the downward projections engage the ground and provide traction.
The moderator plate is generally contoured to conform to the shape of the foot, particularly the sole of the foot, and includes a raised heel region and a lower forefoot region. In addition, the moderator plate includes a raised area for supporting the arch.
The traction plate may be configured for use during a plurality of activities. When configured for use during long distance track and field running events, the traction plate may have a high density of upward and downward projections in the heel and forefoot regions. Projections in these regions ensure that the wearer has sufficient traction when the heel region makes contact with the ground and when the forefoot region disengages the ground. In addition, the projections attenuate impact forces and absorb energy. The traction plate may also include tip members that are attached to the distal points of the downward projections to enhance traction on specific surfaces.
The tips of the upward projections may be attached to the lower surface of the moderator plate. This configuration forms a void between the moderator plate and the traction plate. Whereas conventional sole structures include a foam midsole, an outsole, and additional elements, the sole of the present invention includes the moderator plate and traction plate. The sole structure of the present invention provides a lightweight article of footwear, when compared to conventional footwear, that may be configured for use during a variety of athletic or non-athletic activities.
The advantages and features of novelty characterizing the present invention are pointed out with particularity in the appended claims. To gain an improved understanding of the advantages and features of novelty, however, reference may be made to the following descriptive matter and accompanying drawings that describe and illustrate various embodiments and concepts related to the invention.